Hydraulic apparatus



March 5,1968 LM GDEN ETAL 3,371,611

HYDRAULIC APPARATUS Filed Aug. 31, 1965 RATION 50 E VENTOR.

LARR OGDEN BOYD A. WISE A TTOR/VEY United States Patent 3,371,611 HYDRAULIC APPARATUS Larry M. Ogden and Boyd A. Wise, Penfield, N.Y.,

assignors to General Dynamics Corporation, a corporation of Delaware Filed Aug. 31, 1965, Ser. No. 483,942 3 Claims. (Cl. 103--53) ABSTRACT OF THE DISCLOSURE An apparatus for developing a modulated jet stream output which comprises a chamber which is filled by a fluid source, inlet means disposed between the fluid source and the chamber which have a high impedance to modulated fluid flow, but a low impedance to steady state flow, so that when a piston in the chamber operates to develop a modulated jet stream, the fluid source is efiectively decoupled from the chamber.

The present invention relates in general to hydraulic apparatus and more particularly to apparatus for generating a high power pulsating jet stream.

Although the present invention is suited for more general applications such as in placer mining, cleaning, and chemical milling, it is particularly adapted for stripping bark oil a log. Hydraulic bark strippers are well known to those skilled in the art. High pressure jets of fluid have been used in the past to strip bark off a log. The high pressure jets have been applied to a log which may be rotated and moved longitudinally. Such hydraulic bark strippers have, however, not been adapted to efliciently utilize the hydraulic energy applied thereto. 7

Accordingly, it is a primary object of the present invention to provide an improved hydraulic apparatus that will strip bark off a log in a more economical and eflicient manner.

It is another object of the present invention to provide an improved hydraulic apparatus that produces a higher power fluid jet stream than the prior art.

It is still another object of the present invention to provide a hydraulic apparatus which produces a modulated or pulsating high power jet stream, especially suitable for use in applying hydraulic energy for removing material from a member, such as in bark stripping, placer mining, milling, and the like.

It is still another object of the present invention to provide a hydraulic apparatus whichproduces a' modulated high power jet stream in pulse form which may resemble fluid bullets.

It is still another object of the'present invention to provide an improved hydraulic apparatus which is economical to build, has few moving parts, and is relatively easy to manufacture.

Briefly described, an embodiment of the invention comprises a housing having a chamber and inlet means connected to the chamber for the flow of a high pressure fluid therethrough. The inlet means has a high AC (alternating current) impedance to a modulated fluid flow, buta low DC (direct current) impedance to a steady flow-offluid into the chamber. Further included is outlet means connected to the chamber for the flow of the fluid from the chamber to a load which may be, for example, a log ready for stripping. The outlet means has a lower AC impedance to a modulated fluid flow within the chamber than the inlet means. Also included is a vibration impact generator for modulating the fluid pressure within the chamber.

More particularly, the inlet means may, for example, comprise a plurality of relatively small slender ducts which terminate in ports communicating with the chamber so as to provide a high AC impedance to a modulated or AC fluid flow, but a relatively low DC impedance for a steady or DC fluid flow. The outlet means includes a channel or bore which is large in cross sectional area compared to the plurality of small ducts communicating with the chamber so that the AC impedance of the outlet means to the modulated or AC fluid flow is relatively small in comparison to the AC impedance of the inlet means.

A vibration impact generator, such as a hydroacoustic vibration generator is coupled to a piston slideably disposed within the chamber for generating a modulated or AC fluid flow within the chamber. The vibration impact generator cyclically increases the pressure within the chamber and causes the fluid within the chamber to pulsate at the same frequency at which the vibration impact generator operates. Since the AC impedance of the outlet means is comparatively smaller than the AC impedance of the inlet means to a pulsating or modulated fluid flow, fluid flows through the outlet means in a pulse like manner wherein each pulse generated within the chamber has a higher AC pressure than the DC pressure of the fluid pressure source.

A feature of the invention is that the inlet means and the outlet means each have an AC impedance relationship resulting in the need for few moving parts to derive a modulated jet stream which may be in the form of a high pressure pulsating fluid flow or fluid bullets."

The invention itself, both as to its organization and method of operation, as well as additional objects and advantages thereof, will become more readily apparent from a reading of the following description in connection with the accompanying drawings in which the sole figure is a perspective view, partly in cross section, of the hydraulic apparatus embodying the invention.

In the drawing, hydraulic apparatus 10 is connected to a source of pressurized fluid such as a pump 11 through a pipe 12 at an inlet connection 13. The hydraulic apparatus 10 includes a housing 14 having a cylindrical chamber 15 and a piston 16 slideably disposed within the chamber and forming an end boundary at one end of the chamber 15. The other end of the chamber 15 is terminated by an outlet means 17 for the flow of fluid from the chamber 15 to a load which may be, for example, a log (not shown) ready for bark stripping. The present invention is, of course, not limited for use only in bark stripping but is also useful for other operations wherein a modulated or pulsating stream of high pressure fluid is required.

The hydraulic apparatus 10 further includes an inlet means 18 within the housing 14 and connected between the inlet connection 13 and the chamber 15 for the flow of fluid therethrough. The inlet means 18 includes a plurality of relatively small inlet ports 19 each connected to an annular header or chamber 20 through slender ducts 21 which communicate with the chamber 15. The inlet means 18 has a low impedance to a steady or DC fluid flow such as provided by the pump 11. The inlet means 18, however, has a relatively high impedance to a modulated or pulsating or fluid flow which may be produced when the piston 16 is moved in a reciprocating manner within the chamber and at a given frequency in a manner to be described hereinafter. The structure of the inlet means 18 thus provides for the easy flow of a steady or DC fluid flow into the chamber 15 but offers a high impedance for a modulated or AC fluid flow within the chamber 15. This, of course, provides a means for quickly filling the chamber 15 after the piston 16 has been moved to the right and fluid has been discharged through the outlet means 17. The DC fluid flow through the inlet means 17 also pushes the piston 16 outwardly so that the chamber 15 may be recharged with fluid. During any modulation or rapid changes in pressure within the chamber, back flow of fluid from the chamber 15 through the inlet means 18 is minimized since the outlet means 17 has less AC impedance to a modulated fluid flow than the inlet means 18, as will be described hereinafter, so that a major portion of the AC fluid flow within the chamber 15 is delivered to the load through the outlet means 17.

The outlet means 17 includes a channel or bore 22 connected between the chamber 15 and the load. The bore 22 has a cross sectional area and length such that the combined areas and length of the plurality of the ports 19 and ducts 21 provide the aforesaid impedance ratios.

The hydraulic apparatus also includes a vibration impact generator 25 which may be, for example, a hydroacoustic vibration impact generator 25 which may be operated hydraulically from the pump 11, or it may be any of the well known vibration impact generators which delivers high energy at a relatively short stroke to the piston 16. Reference may be had to Patents Nos. 3,004,- 512; 3,105,460 or 3,143,999 for a description of hydroacoustic vibration generators. The vibration impact generator 25 includes a ram piston 26 which delivers the high energy strokes to the piston 16. The vibration impact generator 25 and the housing 14 are mounted on a base 27 in cooperative relationship so that a small gap exists between the ram piston 26 and the piston 16 between strokes. This, of course, enables an impact to take place during each power stroke. The ram piston 26 and piston 16 may be joined as a single unit to produce a continuous modulated fluid flow. The housing 14 includes a stop 27 for limiting the travel of the piston 16 when it moves in the outward direction to a cocked position, that is, the position in which the ram piston 26 delivers the impact momentum to the piston 16. The piston 16 is repeatedly returned to the cocked position after each power stroke by the DC fluid flow in the chamber 15.

The hydraulic circuit of the hydraulic apparatus 10 may be traced from the pump 11 to the pipe 12 through the inlet connection 13 to the header or chamber 20 of the inlet means 18. Fluid flows from the header or chamber 20 through the ducts 21 and ports 19 into the chamber 15. From the chamber 15, fluid flows through the outlet means 17 to the load.

In the operation of the hydraulic apparatus 10, the frequency of operation may be determined by the vibration impact generator 25. The frequency of operation may be in the range of several cycles per second to several thousand cycles per second. Considering first the quiescent state, fluid is pumped from the pump 11 through the pipe 12 in the chamber through the inlet means 18. The chamber 15 is filled with fluid and remains filled because of the static pressure at the inlet ports and the DC impedance of the outlet means 17. Fluid flows from the chamber 15 through the outlet means 17 to the load. In the quiescent state, a steady flow of fluid will flow through the outlet means 17 in a steady stream manner.

During normal operation of the hydraulic apparatus 10, the vibration impact generator 25 delivers high energy short strokes to the piston 16 by way of the ram piston 26. The ram piston 16 increases the fluid pressure within the chamber 15 during each power stroke cyclically at the frequency determined by the vibration impact generator 25. The reciprocating vibration of the piston '16 causes the pressure of the fluid to vary in amount proportional to the energy delivered to the piston 16 by the vibration impact generator 25. The fluid within the chambers thus goes through cyclic increases in pressure followed by a decrease in pressure whereby the fluid pressure within the chamber 15 is modulated. Thus the steady or DC fluid flow from the pump 11 is changed into a modulated or pulsating flow within the chamber 15. Since the outlet means 17 has less AC impedance to a modulated or pulsating fluid flow, a major portion of the fluid in the chamber 15 is emitted through the bore 22 to the load. Back flow of fluid from the chamber 15 to the pipe 12 is reduced or minimized by the AC impedance of the inlet means 18. It can thus be seen that as the 'vibration impact generator 25 produces a pulsating or modulated -'flow within the chamber 15, high pressure fluid in pulse From the foregoing description, it will be apparent that there has been provided an improved hydraulic apparatus for generating high power modulated jet stream. While a preferred embodiment of the invention has been described, it will be appreciated that variations and modifications in and to the uses of the invention within the scope thereof will become apparent to those skilled in the art. For example, the inlet means 18 may include a plurality of ports within a given quadrant of the cylindrical chamber 15 instead of being disposed equally along the boundaries of the chamber 15 as shown in the drawing. Accordingly, the following description should be considered merely as illustrative and not in any limiting sense.

What is claimed is:

1. Apparatus comprising (a) a housing having a chamber (b) inlet means including a plurality of relatively .slender ducts connected to said chamber for the flow of a fluid under pressure therethrough,

(c) said inlet means having a high impedance to a modulated fluid flow through said chamber but a low impedance to a steady flow of fluid therethrough,

(d) outlet means having a bore of a given length and cross sectional area connected to said chamber for the flow of said fluid from said chamber to a load,

:(e) said outlet means having a lower impedance to said modulated fluid flow than said inlet means,

(f) vibration impact means including a piston slideably disposed within said chamber for modulating the fluid pressure within said chamber when excited into vibrations, and

(g) a hydroacoustic vibration generator included in said vibration impact means.

2. Apparatus comprising (a) a housing having a cylindrical chamber and a header chamber spaced therefrom,

(b) inlet means formed in said housing including a plurality of relatively slender ducts connecting said chambers, said inlet means having a relatively low impedance to a steady flow of fluid therethrough,

(c) a source of pressurized fluid connected to said header chamber,

(d) vibration impact means including a piston slideably disposed within said cylindrical chamber for modulating the fluid pressure within said cylindrical chamber when excited into vibration,

(e) outlet means connected to said chamber and having a substantially lower impedance to the modulated tfluid pressure Within said cylindrical chamber than said inlet means,

(f) said vibration impact means including a ram ele ment for delivering high energy impact strokes to 'said piston, said ram being disposed so that a small gap exists between said ram and said piston in between energy impact strokes.

3. The invention as set iorth in claim 2 including a hydroacoustic vibration generator adapted to drive said ram element in the sonic frequency range.

References Cited UNITED STATES PATENTS FOREIGN PATENTS 5/ 194 1 Germany. 2/1961] Italy.

5/ 1952 Switzerland.

HENRY F. RADUAZO, Primary Examiner. 

